Method and apparatus for drying inked impressions



April 1938. E. M. RICHARDSON 2,113,770

METHOD AND APPARATUS FOR DRYING INKED IMPRESSIONS Filed March 15, 1954 2Sheets-Sheet 1 April 12, 1938. E. M. RICHARDSON METHOD AND APPARATUS FORDRYING INKED IMPRESSIONS Filed March 15, 1934 2 Sheets-Sheet 2 PatentedApr. 12, 1938 METHOD AND mm'rus roa DRYING mxnn macssrons Elmer M.Richardson, East Cleveland, Ohio, assignor to Steel Engravers ApplianceCorporation, Cleveland, Ohio, a corporation of Ohio Application March15, 1934, Serial No. 715,641

4 Claims.

This invention relates to a method and apparratus for rapidly dryinginked impressions on paper, cardboard or similar materials. Moreparticularly, the invention concerns an apparatus for drying impressionsmade from steel engravings on mechanically operated steel die embossingor plate presses.

At the present time practically .all drying of impressions, made bysteel die presses, is accomi plished by lengthy exposure of theimprinted paper sheets to the influence of the atmosphere in theprinting or engraving shop. Each piece of imprinted paper, after beingremoved from the press by the press operator, is individually laid iupon drying racks or trays by another operator. The sheets remain onthese trays untouched until the ink is completely dried by the influenceof the atmosphere. This natural drying process requires from three totwenty-four hours depending on the amount and grade of ink used thegrade and surface characteristics of the paper, and the humidity andtemperature of the atmosphere in the shop. When the ink has dried, thesheets none of which were superimposed upon the other, are manuallygathered from the trays and boxed for shipment, or in case of two ormore color work, the sheets are returned to the press for the secondcolor and the drying process again repeated before the final boxing andshipment can be accomplished.

While the impressed sheets are drying, they remain unstacked on thetrays, as no stacking, even that of placing a single sheet on top ofanother, can be done until the ink is thoroughly 5 dry, otherwise thewet impression will offset on the back of the superimposed sheet.Likewise, in the case of two, (or more), color work, the sheets cannotbe'subjected to a second impression until the previously imprinted inkis dry,

U as the impression will smear on contact with the die, or during thehandling of the sheet. In

either of these instances, that is, when the ink either offsets orsmears. the sheet or sheets are marred and become unfit for presentationto, or

5 acceptance by the customer.

The natural drying process heretofore ,described, requires'largeexpenditures for equipment such as racks and trays. as well as the useof considerable floor space for the storage of i sheets during thedrying process, and for the per cent of the total time required tocomplete the work, and due to the manual labor required, i represents aconsiderable part of the ultimate storage of trays. Likewise the timerequired for such method of drying is at least seventy-five Y cost ofthe product. Nevertheless this natural drying method has been, since theconception of the art of steel engraved printing, practically the onlysuccessful method of accomplishing this essential operation.

There are several requisites for the successful drying of inkedimpressions such as those made by the steel engraving or similarprocesses. Among these is the requirement for virtually completehardening of the ink or pigment to prevent oifsettingor' smearing; Thisrequirement alone eliminates, for all practical purposes the use ofheaters andv the like as are commonly used in ordinary printingprocesses. This is due to the fact that the amount of ink used in theprocess of steelengraving leaves an impression of, considerable weightand thickness as distin guished from the comparative thin film of inkdeposited by ordinary printing presses. Hence to complete the hardeningof the ink or pigment is an object of the present invention.

Another requirement, that must be met to successfully dry theseparticular types of inked impressions, is that of avoiding microscopicor macroscopic changes in the physical structure of the paper on whichthe impressions are made. The structure of the papers, upon which steelengraving is done, is generally of such delicate nature that exceedinglyslight changes in its composition, such as occur when the moisture, 3within the paper itself, is removed rapidly or unevenly, cause the paperto curl, buckle over its entire width or length, or produce numeroussmall waves in the surface of the sheet. The latter is an effect knownin the trade as cockling. An object of the present invention is,therefore, to overcome such difilculties and yet provide a method andapparatus for quickly drying the inked impressions.

Some paper stocks, notably the heavier ones 4'0 and/0r those of high ragcontent, are more susceptible to curling, while the lighter bonds and/or low rag content papers are more susceptible to cockling. I havefound that curling is largely caused by differences in the temperatureof the gree', is caused by much the same diflerences in temperatures ascauses curling. However cockllng is also caused 'by the unevenapplication of heat over thesurface of the sheet, and by the unequalremoval of moisture. due to variations in the density of the sheet. Thuswhen moisture is removed from. the paper, the loss of weight varies frompoint to point of the sheet and the effect on the sheet is mottling .orcockling. I have found that cockling may be avoided, for all practicalpurposes, if the drying medium is maintained at a low temperature Thistherefore is an object of the present invention.

Another object of the present invention is to overcome the dimcultiesheretofore mentioned by providing an apparatus and method for rapidlydrying steel die embossed impressions, at the lowest possibletemperature of the air in an oven through which the embossed sheetspass, equalizing such temperature and evenly applying. to the paper andto the impression, auxiliary drying agency whileminimizing the length oftime of the exposure of the sheets to the drying medium.

Other objects of this invention will become more apparent from thefollowing description, in which reference is had to a preferred form ofapparatus for drying steel die engraved or similar impressions and theessential characteristics of the invention will be set forth in theclaims.

Referring now to the drawings;

Fig. 1 is a side elevation of my improved, drying apparatus;

Fig. 2 is a vertical transverse section, on an enlarged scale, the planeof the section being indicated by the lines 22 on Fig. l;-

Figs. 3 and 4 are longitudinal sections; on a slightly smaller scalethan Fig. 2 and the plane of the sections being indicated by the lines3-3 and 44 respectively on Fig. 2.

Fig. 5 is a detail partially in section illustrating a modified form ofair circulating duct.

My improved method comprises subjecting the impressed sheet first to atempering agency in the form of radiant heat waves, and subsequently toa drying agency in the form of radiant heat waves, while maintaining theatmospheric temperature surrounding the sheet substantially even byconstantly circulating such atmosphere in a substantially closedcircuit, and directing such circulating medium toward the sheet andbetween the sheet and the source of radiant heating energy.

Referring again to the drawings, I have illustrated a preferred form ofapparatus for carrying out my improved method. As shown I have provideda longitudinally extending ovenlike structure l 0 carried by a suitableframe ll having supporting legs If. The oven, as shown, comprises a pairof longitudinally extending casings H and I5,

provided respectively with a top and bottom wall l6 and H. The uppercasing H has downwardly and outwardly extending side and end walls I 8and i9, while the lower casing I5 is provided with upwardly andoutwardly extending side and end walls and fl respectively. The sidewalls of both casings may be joined to, or supported by the frame Ii inany well known manner, suffice it to say that the casing l4issuperimposed upon the casing I5 to form an ovenlike structure l0,completely closed at its sides and having comparatively smallhorizontally extending slotted openings 22 in its end walls to permitthe passuitable conveyor which progresses the sheets through the oven.In the drawings, the frame II has rearwardly and forwardly extendingarms 24 and 25 which support rollers 26 and 2'! respec-' tively. Theroller 24 lies rearwardly from the oven III a distance slightly greaterthan the length of the longest sheet desired to be dried. The roller 2!lies forwardly of the oven a distance sumcient to permit the dischargeof the sheetinto a suitable bin or stacker mechanism generally indicatedin Fig. 1 at 28. A suitable flexible continuous belt 29 is carried bythe rollers 2i and 21, and serves to support and progress the sheetsthrough the drying oven ill with the inked im-' pression uppermost. Thebelt 28 is preferably made of a comparatively light flexible fabric ormetal which will not collect or retain heat to any great extent andtherefore will not interfere with the maintenance of an even temperaturein the oven. Likewise, for this reason the belt is preferablyperforated. f

The belt 29 is driven to progress the sheets A by a suitable motor 30.As some inked impressions require a longer exposure to the dryingmediums than others, the motor is preferabLv-of one of the well knownvariable speed types, the speed ofwhich is manually controlled by a knobor lever 3| carried by the motor. While the motor I. may be drivinglyattached to either the roller 20 or the roller 21, I find it moreconvenient to connect the motor to the roller 26, at the charging end ofthe oven. In this manner the speed of the belt may readily be adjustedby the press operator without any undue loss of time.

The heating of the oven is preferably accomplished and maintained by twogroups of electric heating elements. The first group is in the rearmost,or charging, end of the oven II, and is chiefly used for supplementarilyheating the oven and tempering the paper as it entersthe oven. Theamount of electrical energy delivered to this group of elements iscontrolled by a thermal switch 36 of any well known type, which actsautomatically to energize or deenergize this group, consequent upon achange in temperature within the oven. The switch 36 is provided with aknob 38 by means of which the temperature of the oven may be varied bythe operator to provide for different types of paper and/or ink.

The second group of heating elements I! are in the rear or discharge endof the oven. This group of heating elements comprise the chief source ofheat for the oven and also supplies the supplemental radiation requiredfor drying the inked impression. This supplemental drying agency ischiefly in the form of radiant energy, for the emission of which theelements are kept at a predetermined temperature. This is in contrast tothe first group of elements which are,automatically energized anddeenergized to maintain an even temperature in the oven. For the bulk ofsteel engraved work I have found that the proper temperature for theheating elements in group 39, that is the second group, is approximately600 degrees Fahrenheit. Whereas the preferable oven temperature variesfrom 100 to 250 degrees Fahrenheit. The latter variation beingaccomplished solely by adjustment of the switch 38 which automaticallycontrols the first group 3! of heating elements.

The drying operation is accomplished mainly by radiant energy from thesecond group of elements. It is well known that the absorption of heatrays will vary with the substance and color of the material exposedtothe rays. The ink or other sorption of the rays by the paper itselfwhich is generally white, or of a comparatively light color.Consequently the use of radiant energy saves the paper stock fromexcessive heat absorption and aids materially in eliminating the curlingan cockling effects, previously described.

Each heating element comprises an elongated flat metallic bar 40, of theusual type, and is preferably adjustably supported at its ends bysuitable posts ll which are carried by plate like supporting members"mounted in the casing l4 and which extend the entire length of the'ovensome distance above the upper stretch of the sheet feeding belt 28. Itwill be noted that each heater extends parallel with the direction oftravel of the paper, as this aids in maintaining an even temperatureover the sheets.

Even distribution of the auxiliary drying agency, since the latter is inthe form of radiant heat waves, is partially accomplished as heretoforementioned by the positioning of the elements 40 with relation to thepaper and the impression. However the distribution of the heat waves isbalanced to a great degree by suitable reflectors which are constructedwitha high degree of mathematical. precision. The I reflectors are shownat 45 in the drawings and comprise inverted, polished or semi-polishedmetal troughs which extend longitudinally from one end to the other ofthe oven casing II. The reflectors extend parallel to the belts 29 andtheir lowermost edges extend some distance below the bottom ofthe-heating elements 40 heretofore mentioned. As shown there are twolongitudinal rows of heating elements 40 and therefore a reflector 45 isprovided for each row, such reflectors being mounted on the supportingplates 42 heretofore mentioned.

One of the essential requisites for the success ful drying of steelengraved work is the maintenance of an even temperature on all sides ofthe sheets. This is partially accomplished by the oven like structure inwhich the drying takes place. However I find that keeping the air in theoven constantly circulating, for all practical purposes, enables themaintaining of a completely even temperature on all sides of the sheet.

As heretofore described the oven I is a substantially enclosedstructure, being open only at its opposite ends, where slotted openings41 are of only sufllc ent size to permit the passage of the belt 29 andthe sheets which are to be dried. To circulate the air in this ovenlikestructure, I prefer to provide a duct or conduit 50, one end of which isin communication with the intake of a suitable motor driven fan 52. Theexhaust of this fan is connected with an opening 53 in the top wall ofthe oven by a suitable conduit or duct 54. In this way a constantcirculation of the air within the oven is accomplished.

A more even circulation is accomplished and a greater eiiiciency of theradiant heat units is pro vided for, by the controlling of the directionof flow of the current of circulating air. I find it preferable to socontrol this circulation that the air is forced downwardly through alongitudi- ,nally extending open'ing toward the longitudinal heatingelements.

As shown in the drawings, the plate like members 42 which carry theheating elements 40 and the reflectors 45 extend longitudinally from endto end of the upper oven casing member ll. Each member or wall 42 isconnected to the adjacent sloping side wall l8 of the oven andexcirculating currents to come in contact with the tends therefromhorizontally inward to a point adjacent the longitudinal center of theoven, where each plate is bent downwardly forming spaced verticallyextending walls 56 which extend downwardly to a point substantiallymidway "between the level of the elements 40 and the belt 29. The walls56 form a downwardly opening restricted passageway 51 which extends fromend to end of the oven. The upper end of this passageway 51 isin'communication with a chamber 58 which in turn is in communicationwith the fan 52 as heretofore described. Thus the circulating air isdirected in a smooth flowing current evenly over the embossed sheets.

While the circulating system is substantially closed nevertheless acertain amount of air escapes and is replenished through the slottedopenings 41 heretofore described. I find however that this change of airis slight and serves a valuable purpose, namely that of assisting in thecontrol of the humidity of the circulating air. However as the moisture,content of this circulating air increases beyond a useful point I findit advantageous to admit air from the exterior to lessen the humidity ofthe air within the oven. This is readily accomplished by means of a ventG0 in the duct 50 which leads from the bottom of the oven to the intakeside of the fan. This vent is normally closed by a suitable valve, suchas is indicated at El, but which may be adjustably opened to change thehumidity of the cir culating air.

As above mentioned I believe the moisture con tent of the circulatingair to be valuable. As, when the air has slightly more moisture in itthan the paper has, substantially no moisture will be removed from thepaper. The ink, however, containing much more moisture than either thecirculating air or the paper, will give up its moisture under theinfluence of the radiant heat waves and the circulating atmosphere.

In Fig. 5 I have illustrated a modified form of air circulating system.This form of the invention is especially well adapted when very heavydies,-slow drying inks and other similar conditions are present, any orall of which require the operation of the forward heating elements-atfull temperature. The circulating atmosphere 'may then become too hot toaccomplish the drying of the ink without detriment to the paperheretofore pointed out. This form of the invention therefore provides amechanism to lower the atmospheric temperature of the circulating air.The temperature of such circulating air is lowered materially by theopening of the valve 6| heretofore mentioned and at the same timeincreasing the speed of the blower fan 52. increases the amount of coolair which is drawn into the system by the fan 52. Likewise by partiallyclosing a suitable valve in the conduit 50, the amount of heated air, inproportion to the amount of cool air, is decreased. This howeverrequires the operation of the fan at a comparatively high rate of speed,which in turn passes the air thru the oven at such speed that thesheets, being dried, are apt to be blown to such This obviously anextent as to be detrimental to the drying of the printed inks.

The use of the duct arrangement as shown in Fig. 5 eliminates anyblowing of the paper due to the increase in velocity of the circulatingair, by by-passing an amount of the circulating air sufficient to reducethe velocity of the air in the oven to normal. As shown in Fig. 5 I haveprovided the duct 54 which forms the passageway for the cirstructedpassage of the circulating air through the passageway or duct 54 and theduct 'III- is closed by a suitable valve member H.

As shown in Fig. 51 may provide the passage 54 with an air conditioningunit of any of the well known types which will act to raise or lower thetemperature of the circulating air as desired, such as for instance aradiator 18 through which the air is forced by the fan 52. Suitableconduits l8 communicate with the radiator and supply it with the desiredcooling medium. The radiator may be of any well known type such as forinstance one which will add moisture to the circulating air for thepurposes heretofore mentioned.

From'the foregoing description, it will be seen that I have providedamethod and apparatus by means of which the drying of impressions made bysteel die embossing and similar processes may be successfullyaccomplished in a short time interval. Experience demonstrating that inoven temperatures of to 250 degrees Fahrenheit, and with a radiantdrying element having a temperature of 600 degrees Fahrenheit, thedrying is successfully accomplished in a time interval ranging from 20to 60 secon By accomplishing th drying in such a brief interval of time,at such comparatively low temperatures accurately controlled and evenlyapplied while maintaining a constant circulation of air, the humidityand temperature of which is controlled, steel die and similar processimpressions have been dried without any detrimental effect upon thepaper, either from discoloration, curling, cockling or other cause, andI therefore have provided an apparatus which greatly reduces the cost ofthis and similar types of printing and which apparatus has the addedadvantage of permitting the delivery of the completed work to thepurchaser in a comparatively short time interval after the order for thework is given to the printer.

Likewise it is evident that by insulating the walls of the lower portionl5 of the oven and eliminating such insulation from -the walls of theupper portion ll of the oven, and passing theprinted sheet through theoven substantially midway between the top and bottom walls thereof, Ihave increased the heat in the lower part of the oven and at the lowerside of the sheet and slightfan, a conduit from the intake of said fanto" the bottom of the oven, and a second conduit from ing anove'n likestructure, means to progress 1y decrease the heat in the upper part ofthe oven thereby bringing about a more even distribution of heat on bothsides of the sheet. Such insulation preferably comprises slab likeformations that cover the inner surfaces of the oven walls", 20 and IIas indicated at l. by dotted lines in Fig. 2. a

I claim: 4 1. An apparatus of the class described, a supporting frame,an elongated ovenlike structure 11 carried by said frame, meansincluding a perforated flexible belt carried by said support to progressinked sheets through said structure from end to end, means to vary thespeed of travel of said belt, heating means at the discharge end of 1said oven to heat the oven and comprising a plurality of longitudinallyextending radiant heaters adapted to act on the inked impression anddisposed to either side of the longitudinal center of the oven abovesaid belt, a second group oi heaters similar to the first named heatersat the charging end of the oven to supplementally heat said oven,thermal responsive means to control said last named heater to maintain asubstantially constant temperature insaid oven, reflectors mounted abovesaid heaters, a power operated the exhaust of said fan to the top ofsaid oven.

2. An apparatus of the class described comprisfreshly printed sheetsthrough said oven substantiallymidway between its top and bottom walls,.means toinsulate the walls of said oven below said sheets to prevent theloss of heat through such walls, and wherein the walls of said ovenabove said sheets are uninsulated to permit the loss of heat and therebyequalize the temperature in the oven on either side of the sheets.

3. A mechanism for drying printed sheets ineluding an elongated ovenlike structure having side, end, topand bottom walls, a conveyor passinglongitudinally through said oven substantially J midway its top andbottom walls, a pair of reflectors disposed above the conveyor andextending from end to end of the structure, heating elements in saidreflectors, the sides of the reflectors extending downwardly beyond thebottommost edges of said elements, said reflectors being spaced mi apartthereby forming a longitudinally extending passageway therebetweenwhereby air may be forced toward the material to be dried on saidconveyor.

4. In a device of the class described, the combination of an elongatedoven, means to progress ink impressed sheets through said oven, saidoven including a pair of side walls sloping upwardly and inwardly overthe progressing means and having a pair of spaced vertical wallsextending longitudinally above said progressing means, heaters mountedin the oven above the progressing means and between said vertical wallsand said side walls, and laying above the lower edge of the verticalwalls, and means to circulate a current of air downwardly between saidvertical walls 65 and outwardly between the progressing means and theheaters toward the side walls of the oven.

ELMER M. RICHARDSON.

